Amplifier energizing system



B. F. MIESSNER AMPLIFIER ENERGIZING SYSTEM Filed July 20, 1929 Jan. 26, 1932.

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Patented Jan. 26, 1932 UNITED STATES PATENT OFFICE lBENJ'AKIN I. HIEBSNEB, 0]? SHORT HILLS, NEW JERSEY, ASBIGNOB, BY HERE ABNOR- MENTS, TO RADIO CORPORATION OF AMERICA, OF NEW YORK, N. Y., A. CORPORA- TION '01 DELAWARE AMPLIFIER ENERGIZIN G SYSTEM Application filed July 20,

This invention relates in eneral to amplifier energizing systems, such as systems for energizing radio receivers constructed as units to be installed in cabinets and like housings utilized as receivers of present-day broadcast programs.

In particular, this invention relates to the energizing of an amplifier system, such as a radio receiver, in which the elements are mounted upon a chassis, and in particular those adapted to be energized from a commercial source of alternating current.

lln alternating current energized types of receivers l have found that although such precautions have been taken as mounting the alternating current energy supply transformer at one end of the chassis while mounting the audio transformers of the system at the opposite end of the chassis, and so orientating the audio transformer with respect to the supply transformer that their fields are at right angles to each other, there is sutlicient flux induced in the audio frequency transformers by the flux from the suppl transformer that there results an apprecia le hum in the output device of the system, such as a loud speaker.

l have found the inability to eliminate this hum by spacing and orientation of elements to be due to what seems to be a distortion of the fiua field of the supply transformer by the usual metallic chassis upon which the various elements are mounted, so that there results a coupling between the supply transformer and the audio frequency transformers irrespective of all practical precautions to eliminate coupling by location and orientation of elements.

It is, therefore, the object of my invention to neutralize this coupling between the supply transformer and the audio frequency transformers, customary in the usual amplifying and radio receiver systems.

lt urther objects will become apparent as the description of the accompanyihg drawing is developed, in which there is diagrammatically shown a chassis, a supply transformer with its associated rectifier and filter system, an audio transformer, a number of vacuum 1929. Serial No. 379,673.

tubes, and an output transformer coupled to an indicator.

Referring particularly to the drawin the chassis, indicated by the legend on the rawing, may be of any shape, either solid or latticed, upon which is mounted an alternating current energy supply transformer ST, the primary of which is provided with a pair of leads 1 and 2 adapted to be connected to a source of commercial alternating current supply, such as a house lighting system. The secondary of this transformer is ro'vided with a plurality of secondaries S 2 and S,, the particular number of which varies with the various types of receivers. I have shown the secondary S as supplying ener to the anodes of a full wave rectifier tube T, the filament of which is su plied with heating current from the secondary S the output terminals of the rectifier, namely the center tap potentiometer CT and the mid point of the secondary S being shunted by the usual filter system indicated at FS.

VT indicates a plurality of amplifier tubes, the filaments of which are sup lied with heating current by the secondary 8 of the supply transformer ST. The space current of the tubes VT is supplied from the filter system FS by a connection from one terminal thereof to the plates of the tubes VT through a potential regulating device, such as R, and by a connection from the other terminal of the filter system FS through a grid biasing re sistance GBR to a center tap potentiometer $12, which shunts the filaments of the tubes Reference character T designates one or a plurality of audio frequency transformers of the usual amplifier system, and in my preferred manner of use of my invention is the first audio frequency transformer of a cascaded amplifier system, the primary AP of which is supplied with audio frequenc currents from the usual detector system f0 lowing a series of cascaded radio frequency amplifier systems. I have shown the secondary AS as connected between the grid of tube VT is maintained by the average platecurrent thereof;

transformer of an amplifier system,.is orientated with respect to the supply transformer ST so that the fields thereof, with respectto the air path, are at substantially right angles to each other. This arrangement is preferable, since direct coupling between the transformers T and ST is reduced to a minimum,

and only the stray field induced in the trans former T by the flux flowing through the chassis requires neutralization.

This stray field I may neutralize by eitherone of two systems, first by connecting a coil L having substantially identical flux characteristics as the stray field of supply trans former ST, in series in the filament circuits of tubes VT. By the proper orientation of by the stray field the coil L withrespect to the transformer T, I have found that it is possible to neutralize all the flux induced in the transformer T of the transformer ST flowing through .the. chassis. Another arflergy supply transformer mounted upon said, chassis, an audio frequency transformer rangement consists .in connecting a coil L similar to the coil L across a primary of the transformer ST and orienting thiscoil with respect to the transformer -T so that any residual coupling existing between the transformers T and ST will be neutralized, the current flowing through the coil L being regulated by a resistance R in series therewith.

Since any number of stages may be used in the audio frequency amp ifier system of a commercial radio broadcast receiver, I do not wish to be limited to the use of but one coil L or one coil L coupled to the first audio transformer, but may couple such coils either singly or in combinationwith the several audio frequency transformers of such a cascaded amplifier system without departing from the spirit of m invention. s

It is to be further un erstood that the series connection of the coil L in the filament circuit of the rectifier HT is within the contemplated scope of my invention in the following claims, wherein the coil L is defined to be within the filament'heating the tubes of the radio receiver. I

Having described my invention what I claim is:

1 1. In an amplifying system the combination of a chassis, an alternating current en- As shown, the transformer T, preferably the first audio.

- with res' circuit of b said chassis, and means operatively asso ciated with said supply transformer and in close proximity to said audio transformer for neutralizing the flux induced in said audio transformer by flux flowing through said chassis from said supply tran former.

V 2. In an amplifying system, the combination of a chassis, an alternating current energy supply transformer mounted upon said chassis, an audio frequency' transformer formin part of an amplifying system carried by sai chassis, and means in close proximity to said audio transformer for neutralizing the fluctuating field couplin be tween said supply transformer and said andio transformer, said. meansconsisting of a coil energized from. oneof the windings of said supply transformer, and so orientated said an 'o transformer by thejflux of said supply transformer is opposed by the flux from said c011. v

3. In'an amplifying system, the combination of a chassis, an alternating current energy supply transformer mounted upon said chassis, an audiofrequency transformer forming part of an am lifying system carried by said chassis, an means in close proximity to' said audio transformer for neutralizing the fluctuatin field couplin between said supply trans ormer and sai audio transformer, said means consisting. of a coil having substantially the same flux variation'characteristics as said supply transformer.

4. In an amplifying system, the combination of:a chassis, an alternating currentenergy supply transformer mounted on said chassis, "an audio frequency transformer forming part of an amplifying systemcarried by said chassis, said supply transformer and said audio transformer aving the axes of theirwindings at substantially right angles to each other whereby the air. path of the flux of said supply transformer upon said audio transformer is reduced to a minimum, and means in close proximity to said audio transformer for neutralizingthe flux induced in said audio transformer b flux flowing through said chassis from sai supply transformer.' I

' 5,. In an amplifying system, the combination, of a chassis, an alternating currentenergy supply transformer mounted on said.

chassis, an audio frequency transformer forming apart of an amplifying system carried by said chassis, said supply transformer and said audio transformer having the axes of their windings at substantially right angles .to each other whereby the air path of the flux of said supply transformer upon said audio transformer is reduced to a minimum, and means in close proximity to said audio lftransformer. for neutralizing the flux induced in said audio transformer by flux flowing t thereto'that the flux induced in lit] dill

through said chassis from said supply transformer, said means consisting of a coil energized from one of the windings of said supply transformer and so orientated with respect to said audio transformer that the flux induced in said audio transformer by the flux flowing through said chassis is opposed by the flux from said coil. 1

t. In an amplifying system, the combination of a chassis, an alternating current energy supply transformer mounted on said chassis, an audio frequency transformer forming a part of an amplifying system carried by said chassis, said transformer and said audio transformer having the axes of their windings at substantially right angles to each other whereby the air path of the flux of said supply transformer upon said audio transformer is reduced to a minimum, and means in close proximity to said audio transformer for neutralizing the flux induced in said audio transformer by flux flowing through said chassis from said supply transformer, said means consisting of a coil having substantially the same flux variation characteristics as said supply transformer.

l. ln a radio receiver unit, the combination of a chassis, an alternating current energy supply transformer mounted on said chassis, a plurality of vacuum tubes and as sociated circuits carried by said chassis and forming a radio receiver including an audio frequency amplifying system including an audio frequency transformer, and means coupled to one of the energizing circuits of said tubes and positioned in close proximity to said amplifier for neutralizing the fluctuating field coupling between said supply trans former and said audio transformer.

ll. In a radio receiver unit, the combination of a chassis, an alternating current energy supply transformer mounted on said chassis, a plurality of vacuum tubes and associated circuits carried by said chassis and forming a radio receiver including an audio frequency amplifying system including an audio frequency transformer, and means, including a coil coupled to one of the energizing circuits of said tubes, located in close proximity to said audio transformer, so orientated with respect thereto that the flux induced in said audio transformer by the flux of said supply transformer is neutralized by the flux from said coil.

9. In a radio receiver unit, the combination of a chassis, an alternating current energy supply transformer mounted on said chassis, a plurality of vacuum tubes and as sociated circuits carried by said chassis and forming a radio receiver including an audio frequency amplifying system, including an audio frequency transformer, and means, ineluding a coil having substantially the same flux variation characteristics as said supply transformer, coupled to one of the energizing circuits of said tubes and located in close proximity to said amplifying transformer, so orientated with respect thereto that the flux induced in said audio transformer by the flux of said supply transformer is neutralized by the flux from said coil.

10. In a radio receiver unit, the combination of a chassis, an alternating current energy supply transformer mounted on said chassis, a plurality of vacuum tubes and associated clrcuits carried by said chassis and forming a radio receiver including an audio frequency amplifying s stem, including an audio frequency trans ormer, and a coil series related in the filament heating circuit of at least one of said tubes and located in close proximity to said audio transformer with an orientation with respect to said audio transformer by which the flux induced in said audio transformer by the flux of said supply transformer is neutralized by the flux from said coil.

11. In a radio receiver unit, the combination of a chassis, an alternating current energy supply transformer mounted on said chassis, a plurality of vacuum tubes and associated circuits carried by said chassis and forming a radio receiver, includin an audio frequency amplifying system, inc uding an audio frequency transformer, and a coil hav ing substantially the same flux variation characteristics as said supply transformer series related in the filament heating circuit of at least one of said tubes and located in close proximity to said audio transformer with an orientation with respect to said audio transformer by which the flux induced in said audio transformer by the flux of said su ply transformer is neutralized by the flux rom said coil.'

12. In an amplifying system the combination of a chassis, an alternating current energy supply transformer mounted upon said chassis, an audio frequency transformer forming part of an amplifying system carried by said chassis, and means including a reactance connected with the primary of the supply transformer for neutralizing the flux induced in said audio transformer by said supply transformer.

13. In an amplifying system the combination of a chassis, an alternating current energy supply transformer mounted upon said chassis, an audio frequency transformer forming part of an amplifying system carried by said chassis, and means including an inductance connected across the primary of the supply transformer for neutralizing the flux induced in said audio transformer by said supply transformer.

14. In an amplifying system the combination of a chassis, an alternating current energy supply transformer mounted upon said chassis, an audio frequency transformer forming part of an ampllfymg system carried by said chassis, and means including areactance connected in the secondary circuit of the supply transformer for neutralizing the flux induced in said audio transformer by said supply transformer.

15. In an amplifying system the combination of a chassis, an a ternating current energy supply transformer mounted upon said chassis, an audio frequency transformer forming part of an am lifying system carried by said chassis, an means including an inductance connected in the secondary circuit of the supply transformer for neutralizing the flux induced in said audio transformer by said supply transformer.

16. In an amplifyin system the combination of a chassls, an a ternating current energy supply transformer mounted upon said chassis, an audio frequency transformer forming part of an amplifying system carried by said chassis, and an impedance connected with said supply transformer and in close proximityto said audio transformer for neutralizing t e flux induced in said audio transformer by said supply transformer.

In witness whereof, I have hereunto subscribed my name this 17th day of July 1929.

BENJAMIN F. MIESSNER. 

